This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2002-211310, filed Jul. 19, 2002, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to an X-ray computed tomography apparatus.
2. Description of the Related Art
An X-ray computed tomography apparatus is intended to provide profile information of an inside of a subject based on an intensity of an X-ray which has passed through the subject, having an important role in a number of practices of medicine including disease diagnosis, treatment, operation planning, etc. At the stage of scanning planning, a tube current-time lapse product (mAs) is determined. A number of conventional X-ray computed tomography apparatus display on a scan planning screen thereof CT Dose Index (CTDI), which indicates a radiation dose defined by the U.S. Food and Drug Administration (USFDA). An operator of the X-ray computed tomography apparatus determines an xe2x80x9cmAsxe2x80x9d value with reference to xe2x80x9cCTDIxe2x80x9d. A specific X-ray computed tomography apparatus displays on its scan planning screen a xe2x80x9cCTDIxe2x80x9d value as well as an image quality evaluation index called an image standard deviation (image SD). The operator determines an xe2x80x9cmAsxe2x80x9d value with reference to xe2x80x9cCTDIxe2x80x9d and xe2x80x9cimage SDxe2x80x9d.
The operator, however, cannot know a so-called low-contrast resolution, which determines a relationship between a certain density of an object and its minimum size that can be identified. The operator, therefore, is required to have skills in order to determine the xe2x80x9cmAsxe2x80x9d value appropriately.
It is an object of the invention to provide an X-ray computed tomography apparatus which enables easy setting of appropriate scanning conditions.
An X-ray computed tomography apparatus according to a first aspect of the invention for reconstructing image data based on projection data acquired by scanning a subject with an X-ray, comprising:
an input device configured to input an expected dose of the X-ray;
a calculator configured to calculate a Dose Efficiency index (DEI) based on the expected dose, the DEI indicating a diameter of a target identified at a predetermined detectability rate and the target having a predetermined CT value difference with respect to a surrounding CT value;
a plan support system configured to build up a scan planning screen on which the input expected dose is contained along with the calculated DEI; and
a display configured to display the scan planning screen.
An X-ray computed tomography apparatus according to a second aspect of the invention for reconstructing image data based on data acquired by scanning a subject with an X-ray, comprising:
an input device configured to input a DEI, the DEI indicating a diameter of a target identified at a predetermined detectability rate and the target having a predetermined CT value difference with respect to a surrounding CT value;
a calculator configured to calculate an expected dose of the X-ray based on the DEI;
a plan support system configured to build up a scan planning screen on which the input DEI is contained along with the calculated expected dose; and
a display configured to display the scan planning screen.
An X-ray computed tomography apparatus according to a third aspect of the invention for reconstructing image data based on data acquired by scanning a subject with an X-ray, comprising:
an input device configured to input an arbitrary detectability rate and a diameter of a target identified with the detectability rate;
a calculator configured to calculate an expected dose of the X-ray based on the input detectability rate and the input target diameter;
a plan support system configured to build up a scan planning screen on which the input detectability rate and the input target diameter are contained along with the calculated expected dose; and
a display configured to display the scan planning screen.
An X-ray computed tomography apparatus according to a fourth aspect of the invention for reconstructing image data based on data acquired by scanning a subject with an X-ray, comprising:
an input device configured to input an expected dose of the X-ray and an arbitrary DEI, the DEI indicating a diameter of a target identified at a predetermined detectability rate;
a calculator configured to calculate a CT value difference with respect to a surrounding CT value of the target so that the input DEI may be realized by the input expected dose of the X-ray;
a plan support system configured to build up a scan planning screen on which the input expected dose of the X-ray and the input DEI are contained along with the calculated CT value or a value derived therefrom; and
a display configured to display the scan planning screen.
An X-ray computed tomography apparatus according to a fifth aspect of the invention for reconstructing image data based on projection data acquired by helically scanning a subject with an X-ray sent from an X-ray tube, comprising:
an input device configured to input a DEI, the DEI indicating a diameter of a target identified at a predetermined detectability rate and the target having a predetermined CT value difference with respect to a surrounding CT value;
a calculator configured to calculate an expected dose of the X-ray which corresponds to each of a plurality of positions so that the input DEI may be maintained at the plurality of positions; and
a controller configured to dynamically alter a tube current of the X-ray tube in accordance with the expected dose of the X-ray calculated at the plurality of positions.
An X-ray computed tomography apparatus according to a sixth aspect of the invention for reconstructing image data based on projection data acquired by scanning a subject with an X-ray, comprising:
a calculator configured to calculate a DEI based on a does of the X-ray, the DEI indicating a diameter of a target identified at a predetermined detectability rate and the target having a predetermined CT value difference with respect to a surrounding CT value; and
a stored data file generator configured to generate a storage data file, the storage data file containing therein the image data along with data relating to the calculated DEI.
An X-ray computed tomography apparatus according to a seventh aspect of the invention for reconstructing image data based on projection data acquired by scanning a subject with an X-ray, comprising:
a calculator configured to calculate a DEI based on a does of the X-ray, the DEI indicating a diameter of a target identified at a predetermined detectability rate and the target having a predetermined CT value difference with respect to a surrounding CT value; and
a print data generator configured to generate print data from the image data and the calculated DEI.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
An X-ray computed tomography apparatus according to a eighth aspect of the invention for reconstructing image data based on data acquired by scanning a subject with an X-ray, comprising:
an calculator configured to calculate a parameter relative to the image data; and
a display configured to display an error range of the parameter to be calculated.